from Part I - Models of Cognitive Aging
Published online by Cambridge University Press: 28 May 2020
Without brain systems that modulate arousal, we would not be able to have daily sleep-wake cycles, focus attention when needed, experience emotional responses, or even maintain consciousness. Thus, it is not surprising that there are multiple overlapping neurotransmitter systems that control arousal. In aging, most of these systems show decline in basic features such as number of receptors and transporters, and sometimes even in neuron count. These declines have the potential to disrupt basic arousal functions. Compensatory increases in activity in some of these systems allow for maintained levels of circulating neurotransmitters in those systems – but at the cost of reduced dynamic range in arousal responses.
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